Formation of 2,6-Naphthalenedicarboxylic Acid by the Co–Mn–Br-Catalyzed Autoxidation of 2,6-Diethylnaphthalene in Acetic Acid
作者:Yoshio Kamiya、Takashi Hama、Ichiro Kijima
DOI:10.1246/bcsj.68.204
日期:1995.1
In order to elucidate the reaction mechanism and the optimum reaction conditions for the formation of 2,6-naphthalenedicarboxylic acid (NDCA), the Co(OAc)2–Mn(OAc)2–NaBr-catalyzed oxidation of 2,6-diethylnaphthalene by molecular oxygen was carried out in acetic acid. The oxidation of the ethyl groups to carboxyl groups proceeded mainly via acetyl groups and partly via 1-hydroxyethyl and 1-acetoxyethyl groups. A synergistic catalytic effect due to Co and Mn acetates was observed not only on the rate of oxidation but also on the selective formation of NDCA. The rate of oxidation was strongly retarded at higher concentrations of the substrate, showing that the naphthalene nucleus terminates the chain reaction step of the oxidation. A high concentration of metal catalyst resulted in an increase of acetoxyethylnaphthoic acid. At the optimum reaction conditions, a nearly 90% yield of NDCA was obtained along with small amounts of substituted naphthoic and trimellitic acids. The differences in the yield of NDCA from 2,6-dimethyl, 2,6-diethyl, and 2,6-diisopropylnaphthalenes were compared under similar reaction conditions and are discussed.
为了阐明2,6-萘二甲酸(NDCA)形成的反应机理和最佳反应条件,Co(OAc)2-Mn(OAc)2-NaBr催化氧化2,6-二乙基萘分子氧在乙酸中进行。乙基向羧基的氧化主要通过乙酰基进行,部分通过1-羟乙基和1-乙酰氧基乙基进行。观察到 Co 和 Mn 乙酸盐的协同催化作用不仅对氧化速率而且对 NDCA 的选择性形成也有影响。在较高浓度的底物下,氧化速率被强烈抑制,表明萘核终止了氧化的链式反应步骤。高浓度的金属催化剂导致乙酰氧基乙基萘酸的增加。在最佳反应条件下,NDCA 产率接近 90%,同时还产生少量取代的萘酸和偏苯三酸。在相似的反应条件下比较并讨论了 2,6-二甲基、2,6-二乙基和 2,6-二异丙基萘的 NDCA 产率差异。